Flame-retardant filament and method of manufacture thereof and protective sleeves constructed therefrom

ABSTRACT

A continuous halogen-free flame-retardant filament and method of forming thereof includes providing MC, a phosphorus compound, and PET, and then, forming a mixture of the MC, phosphorus compound, and PET. And lastly, extruding the mixture to form the halogen-free flame-retardant filament. The filament can be braided, woven or knitted into a variety of fabric constructions, such as, for example, sleeves for protecting wires.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to flame-retardant filaments, and moreparticularly to flame-retardant filaments used as yarn for constructingelongate protective sleeves and to methods of manufacture of thefilaments.

2. Related Art

It is known to manufacture fabrics from flame-retardant yarns, whereinthe fabrics are used to protect items from exposure to flames. Forexample, it is known to construct braided, woven or knitted sleeves fromfire-retardant yarns to protect elongate items, such as wires, containedwithin the sleeves. One known compound which has desirablefire-retardant properties is melamine cyanurate (MC).

The assignee herein is also the assignee of U.S. Pat. No. 6,828,365,wherein MC is compounded with a fire-retardant polyphosphonate fillerand a polymer selected from the group consisting of poly(ethyleneterephthalate) and poly(ethylene naphthalate) and then extruded to forma fire-retardant monofilament. The addition of the polyphosphonatefiller to MC increases the flame-retardancy of the monofilament. Sincepolyphosphonate is fire-retardant as well, it provides the resultingmonofilament with additional fire-retardant properties.

Current commercially available halogen-free flame-retardantpoly(ethylene terephthalate) (FR-PET) is made by adding anorgano-phosphorous compound in the polycondensation stage of the PETpolymerization process, such as in U.S. Pat. No. 4,086,208, which isincorporated herein by reference in its entirety. Unfortunately, theflame-retardant properties of this phosphorus-containing PET (P-FR-PET)does not meet the most stringent flame test requirements. In particular,the burn time and flame spread distance are too long, and it emitsflaming drips.

SUMMARY OF THE INVENTION

An extruded halogen-free flame-retardant filament consists of melaminecyanurate and phosphorus containing fire-retardant poly(ethyleneterephthalate) (MC-P-FR-PET). The filament can be braided, woven orknitted into a variety of fabric constructions, such as, for example,sleeves for protecting wires. The combination of the MC and P-FR-PETprovides the fabric constructed therefrom with excellent flame-retardantproperties while remaining pliable, and thus, the fabrics can be used intight quarters around relatively sharp bends.

Another aspect of the invention includes a method of forming ahalogen-free flame-retardant filament. The method consists of: providingMC and P-FR-PET. Then, introducing the MC with the P-FR-PET to form(MC-P-FR-PET). And lastly, extruding the (MC-P-FR-PET) to form thehalogen-free flame-retardant filament.

In one presently preferred construction, the P-FR-PET is made in apolymerization process, and the MC and P-FR-PET are compounded to form ahomogenous compound, and then extruded to form a continuous filament. Inanother presently preferred construction, the MC can be introduced withan organo-phosphorous compound during a PET polymerization process toform a polymerized FR-PET with (MC+phosphorus) composition, and thenextruded to form a continuous filament.

Another aspect of the invention includes a flexible, fire-resistantfabric sleeve for protecting elongate members. The sleeve is constructedat least in part from fire-resistant yarn consisting of (MC-P-FR-PET).

Accordingly, a halogen-free flame-retardant filament constructedaccording to the invention has excellent flame-retardant properties,consists of minimal compound ingredients, is economical in manufacture,is useful in constructing sleeves, and has a long life in use.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily apparent and appreciated when considered inconnection with the following detailed description of presentlypreferred embodiments and best mode, appended claims and accompanyingdrawings, in which:

FIG. 1 is a flow diagram for a process according to one presentlypreferred embodiment of the invention for manufacturing a halogen-freefire-retardant filament;

FIG. 2 is a flow diagram for a process according to another presentlypreferred embodiment of the invention for manufacturing a halogen-freefire-retardant filament and

FIG. 3 is a schematic perspective view of a sleeve constructed at leastin part from the filament constructed from the method of FIG. 1.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

Referring in more detail to the drawings, FIG. 1 diagrams a method 100for manufacturing a halogen-free flame-retardant filament 102 accordingto one presently preferred embodiment of the invention. The resultinghalogen-free filament 102 consists of melamine cyanurate (MC) 104 andphosphorus containing fire-retardant poly(ethylene terephthalate)(P-FR-PET) 106. The combination of MC 104 and P-FR-PET 106 provide thefilament 102 with excellent fire-retardant properties. As such, thefilament 102 is useful in the construction, such as by braiding, weavingor knitting, of a fire-retardant fabric, wherein the resulting fabriccan be constructed in various forms to provide fire-retardant protectionto components. For example, the fabric is useful in constructing afire-retardant sleeve 108 (FIG. 3) for protecting elongate members, suchas wires, from exposure to flames. It should be recognized that thesleeve 108 can be constructed in any suitable fashion, such as an openconstruction, having a longitudinal access opening, a closedconstruction, and in a self-wrapping or wrappable construction, asdesired. The sleeves are widely useful in a broad array of environmentsand industries requiring protection for wiring from flame, such as inautomotive, aircraft, railway, marine, and aerospace, for example.

The method of manufacture of the halogen-free filament 102 starts withsteps 110 and 112 of providing MC and P-FR-PET. The MC 104 is preferablyprovided as commercially available MC, which is generally available as afine powder. A MC powder having a article size of about 2 μm ispreferred, with the MC 104 having a percent-by-weight content of about5-10 percent relative to the MC-P-FR-PET compound.

The P-FR-PET 106 is also commercially available. Preferably, thephosphorus content is about 3000-8000 ppm in proportion to the P-FR-PET.

In manufacture, the MC powder 104 and the polymerized P-FR-PET 106 arecombined in step 114 to form a substantially homogeneous mixture 116.The mixture 116 of the MC and polymerized P-FR-PET can be compoundedtogether, such as in a twin screw extruder, and then extruded into thecontinuous filament 102. Accordingly, there are no additional fillers,fibers, or the like added to the mixture 116, and thus, the finishedfilament 102 contains only MC 104 and polymerized P-FR-PET 106.

Otherwise, in another aspect of manufacture, rather than compounding theMC with the polymerized P-FR-PET, the MC 104 can be incorporated with anorgano-phosphorous compound 118 during a polycondensation stage 120 in aPET polymerization process to form a polymerized FR-(MC+phosphorus) PETcomposition 116, designated earlier as MC-P-FR-PET. Thereafter, asabove, the MC-P-FR-PET composition can be extruded to form thecontinuous filament 102.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, and any otherclaims allowed which stem from this application, that the invention maybe practiced otherwise than as specifically described and shown.

1. An extruded halogen-free flame-retardant continuous elongatefilament, consisting of: melamine cyanurate; phosphorus compound; andpoly(ethylene terephthalate).
 2. The filament of claim 1 wherein saidphosphorus compound is incorporated in a stage of polycondensation of apoly(ethylene terephthalate) polymerization process to form P-FR-PET. 3.The filament of claim 2 wherein said melamine cyanurate is compoundedwith said P-FR-PET.
 4. The filament of claim 1 wherein said melaminecyanurate and said phosphorous compound are incorporated in a stage ofpolycondensation of a poly(ethylene terephthalate) polymerizationprocess to form MC-P-FR-PET.
 5. A method of forming a halogen-freeflame-retardant continuous elongate filament, consisting of the stepsof: providing melamine cyanurate; providing a phosphorus compound;providing poly(ethylene terephthalate); forming a compound of saidmelamine cyanurate, said phosphorous compound and said poly(ethyleneterephthalate); and extruding said compound to form said filament. 6.The method of claim 5 wherein the forming a compound step includesincorporating said phosphorus compound in a stage of polycondensation ofa poly(ethylene terephthalate) polymerization process to form P-FR-PET.7. The method of claim 6 wherein the forming a compound step includescompounding said melamine cyanurate with said P-FR-PET.
 8. The method ofclaim 5 wherein the forming a compound step includes incorporating saidmelamine cyanurate and said phosphorus compound in a stage ofpolycondensation of a poly(ethylene terephthalate) polymerizationprocess to form MC-P-FR-PET.
 9. A flexible, fire-resistant fabric sleevefor protecting elongate members, comprising: at least one yarn, saidyarn consisting of: melamine cyanurate; a phosphorus compound; andpoly(ethylene terephthalate).
 10. The fabric sleeve of claim 9 whereinsaid at least one yarn is a monofilament.
 11. The fabric sleeve of claim9 wherein said at least one yarn is a multifilament.
 12. The fabricsleeve of claim 9 wherein said phosphorus compound is incorporated in astage of polycondensation of a poly(ethylene terephthalate)polymerization process to form P-FR-PET.
 13. The fabric sleeve of claim12 wherein said melamine cyanurate is compounded with said P-FR-PET. 14.The fabric sleeve of claim 9 wherein said melamine cyanurate and saidphosphorous compound are incorporated in a stage of polycondensation ofa poly(ethylene terephthalate) polymerization process to formMC-P-FR-PET.